Polymer–Nanoparticle Composite Films with Ultrahigh Nanoparticle Loadings Using Capillarity-Based Techniques

Polymer–nanoparticle (NP) composites with ultrahigh loadings (more than 50 vol %) of NPs possess exceptional mechanical, transport, and physical properties, making them valuable for various applications. However, producing such polymer–NP composites poses significant challenges due to difficulties associated with mixing and dispersing high fractions of NPs in polymers. A promising approach to overcome these challenges involves infiltrating a polymer into the interstitial pores of a disordered NP packing, resulting in a polymer-infiltrated NP film (PINF). Recently, versatile capillarity-driven techniques have emerged, successfully enabling the production of PINFs. These capillarity-driven techniques allow for the fabrication of homogeneous (fully infiltrated), nanoporous (partially infiltrated), and heterostructured PINFs. Infiltrating polymers into stiff but brittle NP packings increases their toughness, attributed to the formation of polymer bridges between adjacent NPs or interchain entanglements. The physical confinement of polymer within the interstitial pore also enhances thermal stability and heat transfer of PINFs. Additionally, the tunable nanoporosity and heterostructures of PINFs lead to unique optical properties suitable for various practical applications.